<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    let num1 = +prompt('请输入第一个数字') 
    let n = prompt('请输入运算符（+,-,*,/）')
    let num2 = +prompt('请输入第二个数字') 
    switch(n){
    case('+'): 
    alert( num1+ num2 )
    break
    case('-'):
    alert(num1 - num2 )  
    break
    case('*'):
    alert (num1 * num2) 
    break
    case('/'): 
         alert(num1 / num1) 
    break
    default:
        alert('没有找到')
        break;
    }
    
</script>
</html>